Project Summary Our long-term objective of this proposed research is to discover novel treatments for red cell disorders with hemoglobinopathy. In this proposal, we focus our efforts on the role of translational regulation in ??thalssemia. Thalassemia is the most common monogenic disease in the world, and is emerging as a major economics and health burden in the world. In addition, it is well established and commonly noticed in ??thalssemic patients that the same mutation in ??globin gene may have drastically different clinical outcome. Hem-regulated eIF2? kinase (HRI) is initially discovered to inhibit general protein synthesis in heme-deficiency of erythroid precursors, and thus balances heme and globin synthesis. Recently, our laboratory has reported that HRI is necessary to reduce the severity not only in iron-deficiency anemia,but also in ?-thalassemia. In fact, HRI elicits the most drastic modifier response in mouse models of ?- thalassemia to date. HRI mediates this protection by phosphorylation of eIF2? and inhibition of protein synthesis including ?-globin to prevent ? excessive accumulation of ?-globin aggregates. Thus, HRI and its downstream substrates may be potential ? pharmaceutical targets for the development of novel treatments of severe thalassemia. The specific aims of this proposal are (1) to test and evaluate the feasibility of salubrinal, a small chemical inhibitor specific for dephosphorylation of eIF2?P, in reducing globin aggregation and apoptosis in Hbb-/- ??thalassemic erythroid precursors;and (2) to screen chemical libraries for compounds that modulate HRI stress response pathway and reduce apoptosis of ?-thalassemic erythroid precursors. We will use our compounded mice with deficiencies in HRI and ??major globin genes as a model of a severe form of ?-thalassemia. We will examine whether salubrinal can increase eIF2?P level, decrease ?-globin synthesis and aggregation, and reducing proliferation and apoptosis in mouse thalassemic red cell precursors. We will use arsenite induced cell tocixity as a model system for ??thalassemia to screen for chemicals that will protect the survival of erythroid precursors. The molecular mechanisms by which candidate compounds achieve the protection in ?- thalassemic erythroid will be investigated The outcome of these studies may leads to discovery of novel compounds for treatments of not only thalassemia but also red cell disorders generally. Project Narrative The purpose of this proposed research is to further our understanding of the pathology of anemia caused by mutations in hemoglobin. This study may also lead to the discovery of novel drug treatments for red blood cell diseases.